Geomorphological characterization of endorheic basins in northern Chile

Abstract

Quantitative geomorphology regroups a large number of interesting tools to characterizenatural basins across scales. The application of these tools to several river basins allows the description andcomparison of geomorphological properties at different spatial scales as oppose to more traditionaldescriptors that are typically applied at a single scale, meaning the catchment scale. Most of the recentresearch using these quantitative geomorphological tools has focused on open catchments and no specificattention has been given to endorheic basins, and the possibility of having particular features that distinguishthem from exorheic catchments.The main objective of our study is to characterize endorheic basins and investigate whether these specialgeomorphological features can be identified. Because scaling invariance is a widely observed and relativelywell quantified property of open basins, it provides a suitable tool to characterize differences between thegeomorphology of closed and open basins. Our investigation focuses on three closed basins located innorthern Chile which describe well the diversity in the geomorphology and geology of this arid region.Results show that endhoreic basins exhibit different slope-area and flow paths sinuosity regimes compared tothose observed in open basins. These differences are in agreement with the particular self-similar behavioracross spatial scales of the Euclidean length of subcatchments, as well as the Hack’s law and Horton’s ratios.These regimes imply different physical processes inside the channel network regardless of the basin area,and they seem to be related to the endorheic character of these basins. The analysis of the probability densityfunctions of contributing areas and lengths to the lower region shows that the hypothesis of self-similarity canalso be applied to closed basins. Theoretical expressions for these distributions were derived and validated bythe data.Future research will focus on (1) applying similar analyses in other locations and comparing the results, and(2) understanding and modeling the effects of groundwater in forming the landscape of these arid regions